id,summary,reporter,owner,description,type,status,priority,component,version,resolution,keywords,cc,guest,host
1811,Painfully slow direct I/O on Linux guest,decoder,,"Hello,
after experiencing quite slow I/O in general (Linux/Linux, compact vdi image), I did some experiments. In detail I created a file in the guest that I tried to overwrite with dd using direct I/O (dd if=/dev/zero of=/some.file bs=4M count=1000 conv=notrunc oflag=direct).
This command resulted in a writing speed of ~300 kb/s (yes, kb). The same thing in KVM resulted in a normal writing speed (30-50 mb/s) on a comparable host (although the second one has a slightly faster hdd setup, the hosts aren't the bottlenecks in this case).
Is this a known problem/expected behavior?
I am using Virtual Box 1.6.2 (closed) with the SATA controller.
I posted some more stats here: http://forums.virtualbox.org/viewtopic.php?p=27851#27851 if this is relevant.
If you need further details, feel free to contact me.",defect,closed,major,other,VirtualBox 1.6.2,worksforme,linux direct io performance,decoder@…,other,other